<?php

// Database selector class
class DatabaseConnection extends BaseMiddleware implements DatabaseConnector, LimitableObject {
	// Array for connection data
	private $connectData = array();

	// The real database layer
	private $dbLayer = null;

	// An instance of this class
	private static $thisInstance = null;

	// Private constructor
	private final function __construct() {
		// Call parent constructor
		parent::constructor(__CLASS__);

		// Set description
		$this->setPartDescr("Datenbank-Mittelschicht");

		// Create an unique ID
		$this->createUniqueID();

		// Clean up a little
		$this->removeSystemArray();
	}

	// Create new database connection layer
	public final static function createDatabaseConnection (DebugMiddleware $debugInstance, DatabaseFrontendInterface $dbLayer) {
		// Get instance
		$dbInstance = new DatabaseConnection();

		// Set debug output handler
		$dbInstance->setDebugInstance($debugInstance);

		// Set database layer
		$dbInstance->setDatabaseLayer($dbLayer);

		// Set db instance
		self::$thisInstance = $dbInstance;

		// Return instance
		return $dbInstance;
	}

	// Get an instance of this class
	public final static function getInstance () {
		return self::$thisInstance;
	}

	// Public setter for database connection
	public final function setConnectionData ($login, $pass, $dbase, $host) {
		// Transfer connection data
		$this->connectData['login'] = (string) $login;
		$this->connectData['pass']  = (string) $pass;
		$this->connectData['dbase'] = (string) $dbase;
		$this->connectData['host']  = (string) $host;
	}

	/**
	 * Save a whole object or parts of it to the database or local file
	 *
	 * @param		$object	The object we shall save
	 * @return	void
	 * @throws	NullPointerException	If $limitInstance is null
	 * @throws	NoObjectException		If $limitInstance is not an object
	 * @throws	MissingMethodException	If the required method
	 *								saveObject() was not found
	 */
	public final function saveObject ($object) {
		// Some sanity checks
		if (is_null($this->dbLayer)) {
			// Is null
			throw new NullPointerException($this, self::EXCEPTION_IS_NULL_POINTER);
		} elseif (!is_object($this->dbLayer)) {
			// Is not an object
			throw new NoObjectException($this->dbLayer, self::EXCEPTION_IS_NO_OBJECT);
		} elseif (!method_exists($this->dbLayer, 'saveObject')) {
			// Does not have the required instance
			throw new MissingMethodException(array($this->dbLayer, 'saveObject'), self::EXCEPTION_MISSING_METHOD);
		}

		// For now just pipe it through to the database layer
		$this->dbLayer->saveObject($object);
	}

	/**
	 * Set a limitation for the saving process. This shall be done before
	 * saveObject() is called else saveObject() shall save the whole object.
	 *
	 * @param		$limitInstance	An instance of ObjectLimits which contains
	 *						elements we shall exclusivly include in
	 *						saving process
	 * @return	void
	 * @throws	NullPointerException	If $limitInstance is null
	 * @throws	NoObjectException		If $limitInstance is not an object
	 * @throws	MissingMethodException	If the required method
	 *								limitObject() was not found
	 */
	public final function limitObject (ObjectLimits $limitInstance) {
		// Get real database connection
		$this->dbLayer = $this->getDatabaseInstance();

		// Some sanity checks
		if (is_null($this->dbLayer)) {
			// Is null
			throw new NullPointerException($this, self::EXCEPTION_IS_NULL_POINTER);
		} elseif (!is_object($this->dbLayer)) {
			// Is not an object
			throw new NoObjectException($object, self::EXCEPTION_IS_NO_OBJECT);
		} elseif (!method_exists($this->dbLayer, 'limitObject')) {
			// Does not have the required instance
			throw new MissingMethodException(array($this->dbLayer, 'limitObject'), self::EXCEPTION_MISSING_METHOD);
		}

		// For now we pipe this through to the real database instance
		$this->dbLayer->limitObject($limitInstance);
	}

	/**
	 * Analyses if a unique ID has already been used or not. This method does
	 * only pass the given ID through to the "real" database layer.
	 *
	 * @param		$uniqueID		A unique ID number which shall be checked
	 *						before it will be used
	 * @param		$inConstructor	If called from a constructor or from
	 *						somewhere else
	 * @return	$isUnused		true	= The unique ID was not found in the database,
	 *						false = It is already in use by an other object
	 * @throws	NullPointerException	If $this->dbLayer is null
	 * @throws	NoObjectException		If $this->dbLayer is not an object
	 * @throws	MissingMethodException	If the required method
	 *								isUniqueIdUsed() was not found
	 */
	public final function isUniqueIdUsed ($uniqueID, $inConstructor = false) {
		// Some sanity checks
		if (is_null($this->dbLayer)) {
			// Is null
			throw new NullPointerException($this, self::EXCEPTION_IS_NULL_POINTER);
		} elseif (!is_object($this->dbLayer)) {
			// Is not an object
			throw new NoObjectException($object, self::EXCEPTION_IS_NO_OBJECT);
		} elseif (!method_exists($this->dbLayer, 'isUniqueIdUsed')) {
			// Does not have the required instance
			throw new MissingMethodException(array($this->dbLayer, 'isUniqueIdUsed'), self::EXCEPTION_MISSING_METHOD);
		}

		// Pass the returning result through
		return $this->dbLayer->isUniqueIdUsed($uniqueID, $inConstructor);
	}	

	/**
	 * Gets cached data from the database layer and if not found fetch it from
	 * the database again. This method does not return the header stuff because
	 * The underlaying database class will return only the requested content.
	 *
	 * @param		$idNumber		The ID number which we need for looking up
	 *						the requested data
	 * @return	$cachedArray	The maybe cached data from the database
	 * @throws	NullPointerException	If $this->dbLayer is null
	 * @throws	NoObjectException		If $this->dbLayer is not an object
	 * @throws	MissingMethodException	If the required method
	 *								isUniqueIdUsed() was not found
	 */
	public final function getObjectFromCachedData ($idNumber) {
		// Some sanity checks
		if (is_null($this->dbLayer)) {
			// Is null
			throw new NullPointerException($this, self::EXCEPTION_IS_NULL_POINTER);
		} elseif (!is_object($this->dbLayer)) {
			// Is not an object
			throw new NoObjectException($object, self::EXCEPTION_IS_NO_OBJECT);
		} elseif (!method_exists($this->dbLayer, 'getObjectFromCachedData')) {
			// Does not have the required instance
			throw new MissingMethodException(array($this->dbLayer, 'getObjectFromCachedData'), self::EXCEPTION_MISSING_METHOD);
		}

		// Pass the returning result through
		return $this->dbLayer->getObjectFromCachedData($idNumber);
	}

	/**
	 * Setter for the real database layer
	 * @param		$dbLayer		An instance of the real database layer
	 * @return	void
	 */
	public final function setDatabaseLayer (DatabaseFrontendInterface $dbLayer) {
		$this->dbLayer = $dbLayer;
	}
}

// [EOF]
?>